Liquid metering system

Abstract

A pump device for metering and/or feeding liquid materials, particularly colorants and plasticizers for molded plastics. The pump consists of a linear metering tube which is straight throughout of length of the compression zone, thereby reducing stress and fatigue on the tube, thus prolonging tube life. The metering tube is compressed by compression rollers attached to an endless drive belt which moves within a track cut into a housing. In another embodiment of this invention, wherein the linear metering tube is inclined slightly, stresses on the tube are distributed over the tube by the gradual compression of the tube. The pump provides for simple, precise, long-life dispensing of polymer additives.

We claim: 
     
       1. A pump for liquid material comprising: a housing;   a track cut into said housing, wherein said track forms a loop;   a support plate cut into said housing, said support plate having a first end and second end, said support plate is inclined over the entire length from said first end to said second end, wherein said incline is at a fixed angle of from about 1° to about 9°;   a channel formed into said support plate;   a retainer bracket attached to said housing within said track and having a top edge, a bottom edge, a front surface, and a back surface;   an open-ended, elastic-walled hollow tube for receiving liquid material, held in said channel formed into said support plate and supported by said support plate, said tube having an open feed end and an open discharge end; and   a power-driven assembly positioned adjacent the length of said tube comprising, a power-driven drive wheel, a free-moving wheel, spaced compression rollers mounted on an endless, flexible drive belt traveling within said track wherein said flexible drive belt passes around the outside of said drive wheel and said free-moving wheel and is engaged by said wheels such that movement of said drive wheel will move said flexible drive belt; said angle taken with respect to said belt at a location adjacent said support plate; said compression rollers which, in repeating cycles, engage said tube at a first contact point to gradually collapse a portion of the tube between said compression roller and said support plate starting at said first contact point of said tube and working progressively toward the discharge end where it disengages said tube at a second contact point of said tube and discharges the material from the tube, wherein at least one edge of said tube is inclined at the same angle as the support plate for at least a portion thereof between said feed end, adjacent said first contact point, and said first contact point, and between said first contact point and said second contact point, and between said first contact point and said second contact point, and wherein said retainer bracket provides support for said drive belt engaging said tube.   
     
     
       2. A pump of claim 1 wherein at least one edge of said tube is inclined at the same angle as the support plate for at least a portion thereof between adjacent said second contact point and said discharge end of said tube. 
     
     
       3. The pump of claim 1 wherein said power driven wheel is a sprocket. 
     
     
       4. The pump of claim 1 wherein said free-moving wheel is a sprocket. 
     
     
       5. The pump of claim 1 wherein said support plate is inclined from about 4° to about 6°.